Synthesis and photoluminescence properties of poly(1-hexyl-2-aryl acetylene)s, poly(1-phenyl-2-fluorenylacetylene), and poly(1-fluorenyl-2-fluorenlacetylene)

The metathesis polymerizations of 1-hexyl-2-arylacetylenes [n-C6H13CCAr; Ar = phenyl (1a), naphthyl (1b), biphenyl (1c), fluorenyl (1d)] were examined using NbCl5, TaCl5, and WCl6. When NbCl5/n-Bu4Sn was used as a catalyst in their polymerization, high-molecular-weight polymers (2a–2d) were obtained in good yield compared to TaCl5/n-Bu4Sn and WCl6/Ph4Sn. 1-Hexyl-2-[2-(9,9-dialkylfluorenyl)]acetylenes (1e–1h) also polymerized by NbCl5/n-Bu4Sn to give corresponding polymers (2e–2h) with relatively high molecular weights. Diarylacetylene polymers (2i and 2j) were obtained by the metathesis polymerization using TaCl5/n-Bu4Sn. All the poly(1-hexyl-2-arylacetylene)s (2a–2h) emitted blue-colored lights, and the fluorenyl group-containing polymers exhibited strong photoluminescence. However, the fluorenyl group-containing polymers with long alkyl groups such as n-butyl and n-octyl groups at the 9-position on fluorene rings showed weak emissions because the steric hindrance of long alkyl groups prevents to form intramolecular excimers. The emission spectra of diarylacetylene polymers red-shifted, and 1-phenyl-2-[2-(9,9-dimethylfluorenyl)]acetylene (2i) and 1-(2-fluorenyl)-2-[2-(9,9-dimethylfluorenyl)]acetylene (2j) showed green-colored and yellow-colored emissions, respectively.

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► Novel poly(1-hexyl-2-arylacetylene)s and poly(difluorenylacetylene) were synthesized.
► Poly(substituted acetylene)s having fluorenyl groups showed strong emissions.
► The effect of alkyl substituent on polymer's fluorescence was revealed.
► Three types of polymers emitted blue, green, and yellow lights, respectively.